1. Field of the Invention
The present invention relates generally to a library device, and more particularly to an accessor hand mechanism in a library device.
2. Description of the Related Art
A library device is a device for containing a plurality of information recording medium cartridges such as optical disk cartridges or magnetic tape cartridges, loading a selected one of the cartridges into a drive unit, and reading/writing information from/to the medium. In recent years, an optical disk library device in particular has been increasingly demanded for data retrieval requiring a large storage capacity as in retrieving multimedia, image data, graphic data, etc., and it is desired to provide a mass-storage optical disk library device which can be installed in a small space and can contain more optical disk cartridges.
In general, an optical disk library device is composed of a cartridge access station (CAS) for loading and unloading an optical disk cartridge into and from the library device, a cell drum having a plurality of cells each for containing the cartridge, a drive unit for reading and writing data from and to a recording medium contained in the cartridge, and an accessor for carrying the cartridge between the cartridge access station, the cell drum, and the drive unit. Such an optical disk library device has recently been used as an external mass-storage device for a computer, and the library device is required to reliably even without operator intervention.
The accessor is provided with a hand unit or hand mechanism vertically movable along a guide shaft, and the hand unit has a pair of fingers for gripping the cartridge. The hand unit is required to perform an operation for opening and closing the fingers, and a slide operation for advancing and retracting the fingers. A conventional accessor hand unit employs a plurality of motors dedicated for these operations.
That is, a plurality of motors are mounted on an accessor mechanism portion designed to be vertically moved, causing an increase in weight and capacity of the accessor. In the conventional accessor, a driving power of about 150 watts is necessary for a motor for vertically driving the accessor mechanism portion. In the conventional accessor hand unit, the fingers and a portion for pushing the cartridge interfere with a front panel of the drive unit, and the cartridge cannot therefore be carried to a loading position of the drive unit.
Accordingly, in the case where general inexpensive drive units not specially developed for the library device are mounted in the library device, it is necessary to mount a cartridge transfer mechanism for each drive unit, causing a considerable increase in cost. Further, in the conventional accessor, a vertical sliding portion of the accessor and a base of the hand unit are integrated. With this integral structure, every time maintenance and replacement of the hand unit are required, a side panel and an upper panel of the library device must be removed to take out the guide shaft. Thus, the conventional accessor has a problem in maintainability such that the maintenance and replacement of the hand unit cannot be performed in the field, or much time for maintenance is necessary.
On the other hand, in the case where drive units specially developed for the library device are used, the cartridge can be directly transferred between the accessor and each drive unit. However, as the cartridge is forcibly ejected from the drive unit by the action of an eject spring, the cartridge is allowed to be ejected only when the accessor has reached the front side of the drive unit.
In other words, if the cartridge is forcibly ejected from the drive unit in the condition where the accessor is absent on the front side of the drive unit, the cartridge jumps out of the drive unit to possibly block the path of the accessor. Therefore, in general, the cartridge is allowed to be ejected only when the accessor has reached the front side of the drive unit.
If no cartridge transfer mechanism is provided between the accessor and each drive unit as mentioned above, even after completing the read/write process or the like in the drive unit, the ejection of the cartridge from the drive unit must be delayed until the accessor reaches the front side of the drive unit. As a result, an access time becomes long.
Further, drive control means for the accessor must grasp the control circumstances (completion, error, etc. of the eject operation) of drive control means for the drive unit during the control operation of the accessor, while the drive control means for the drive unit must monitor the arrival of the accessor at the front side of the drive unit in performing the eject operation. Thus, the control means in the library drive are complex.